Zimbabwe's ruling party has said that a second round of presidential elections could be delayed by up to a year in a move that would extend Robert Mugabe's rule even though he admits to having lost the first round of voting five weeks ago.

The election commission is expected to meet soon to set a date for the run-off vote between Mugabe and the opposition candidate, Morgan Tsvangirai. The law required it to have been held within three weeks of the original election, but the commission has the power to extend the period between the votes.

The deputy information minister, Bright Matonga, said at the weekend that the run-off might take place in three weeks, but could take up to a year, suggesting that Zanu-PF remains concerned at Mugabe's ability to win, despite a state-sponsored campaign of violence and intimidation against the opposition.

Mugabe won only four out of 10 votes in the first round, according to the election commission, leaving him with a considerable task to win the run-off. The election commission gave him 43.2% of the vote to 47.9% for Tsvangirai of the Movement for Democratic Change.

While it is not clear whether Matonga was speaking with Mugabe's authority in suggesting a long delay, political analysts in Zimbabwe say Zanu-PF is not in any hurry for another election.

The opposition also fears that spreading political violence will provide a pretext for Zanu-PF to drag out the election further on the grounds that there is too much instability to hold another vote, even though the ruling party is principally responsible for creating the upheaval.

Thousands of people have been beaten, thousands more driven from their homes and about 20 murdered, according to the opposition, in an army-led campaign of violence focused on rural areas where the opposition performed well.

Yesterday, Zimbabwe's teachers union threatened a national strike unless the government stops attacks on teachers who acted as election officials. The union said 1,700 teachers had fled their homes and hundreds more had been arrested to deter them from overseeing the next election because they were neutral.

Meanwhile, the MDC is wavering over its previous refusal to take part in a second round after calling the results "scandalous daylight robbery". It said Tsvangirai won the presidential election outright with 50.3%, based on returns from each polling station. It accused the government of altering the results by 87,000 votes in favour of Mugabe to force Tsvangirai below the 50% mark to avoid a run-off.

However Tsvangirai risks looking as if he is unwilling to compete if he shies away from a run-off, and could hand victory to his rival by default.

The US and other western governments have warned that state-sponsored violence against activists and voters since the first round of elections has made a democratic run-off impossible. They have been joined by groups such as Human Rights Watch, whose Africa director, Georgette Gagnon said: "The ruling party's bloody crackdown makes a free run-off vote a tragic joke."

The Roman Catholic church in Zimbabwe yesterday called on the UN and African Union to supervise the next ballot. In a statement read to Sunday services, it said the state election commission could not be trusted to be neutral, because it took five weeks to release the results of the first round.

With the economy in tatters, there is also the question of cost. The former finance minister, Simba Makoni, who ran a poor third in the presidential race, said Zimbabwe could not afford another election and a power-sharing deal had to be negotiated.